Burner control system



April 13 1937. B E SHAW 2,@7fi,963

' BURNER CONTROL SYSTEM Filed Jan. 6, 1956 UNITED @FFICE.

attests BURNER (CGNTRUL srs'rsM Burton E. Shaw, Adel, liowa, assignor to Penn Electric Switch Company, Des Moines, llowa, a

corporation of Iowa Application January 6, 1936, Serial No. 57,?35

12 Claims.

An object of my invention is to provide a burner control system which is inexpensive to manufacture and simple in operation and arrangement of parts.

A further object is to provide a controller including burner contacts and safetyswitch contacts, both operable from a single actuator, thus eliminating a relay and to provide a combustion temperature responsive means associated with the controller for modifying the operation of the burner and safety switches by the actuator.

A further object is to provide a heat responsive actuator for first closing a normally open burner switch and then opening a safety switch, combustion temperature actuated means being operable to arrest the movement of the actuator after the burner switch is closed, provided combustion is successfully established.

Another object is to provide a controller in which a resistance or heating element effects operation of a warp element or the like, a shield being interposable between the two to prevent operation of the actuator in accordance with certain conditions.

A still further object is to provide a shield so constructed that it refiectsthe heat from the heating element and absorbs heat from the actuator, the degree of absorption and reflection being predetermined, depending on requirements for 30 the various installations.

With these and other objects in view, my invention consists in the construction, arrangement and combination of the various parts of the device, whereby the objects contemplated are 35 attained, as hereinafter more fully set forth, pointed out in my claims,and illustrated in the accompanying drawing, in which:

Figure 1 is a front elevation of a controller used in my burner control system.

Figure 2 is a vertical sectional view on the line 2-2 of Figure 1, showing the parts on an enlarged scale.

Figure 3 is an enlarged sectional view on the line 3-3 of Figure 1.

45 Figure 4 is a diagrammatical view of the parts in Figure 1 in a different position.

Figures 5 and 6 are similar diagrammatical views, showing still different positions; and

Figures '7 and 8 are electrodiagrammatical 50 views showing the control system adapted for low voltage and highvoltage room thermostat circuits respectively.

On the accompanying drawing I have used the reference numeral ID to indicate a switch casing.

55 Within the casing ID a base l2, preferably of insulation, is provided for mounting the various elements of the controller. A tube l4 extends from the rear of the casing it for extension into a stack or other portion of a furnace, so that a bimetal element it, carried by the inner end of 5 the tube l4, may respond to combustion temperatures.

The bimetal element i6 is U-shaped and anchored at one end to a stationary lug iii, an arm Zll being secured to the other end of the bimetal element to secure magnification of the motion thereof.

The arm ill extends through a slot 22 in the casing it, and a slot 24 in the base 62, to a position within the casing ll]. Within the casing it it has 2. depending extension 26 connected to one end of a flexible strap 28. The strap 28 extends around and frictionally engages a spindle 36 of a shield S. The shield S has a second spindle 32, the spindles being mounted in bear- 20 ings 34.

The other end of the flexible strap 28 is connected by a spring 36 to a pin 38. One of the bearings 34 is provided with a pair of stop pins 40 and 42. 25

From the construction of the parts thus far described, it will be obvious that upon the temperature rising and the bimetal element I6 opening, the spindle will be rotated clockwise as in Figure 2, for swinging the shield S from the vertical position of Figure 2 to the horizontal position of Figure 3, and from the stop pin 40 to the stop pin 42. Thereafter the arm 20 can move farther, the strap 28 merely slipping relative to the spindle 30.

Upon a subsequent reduction of temperature v affecting the bimetal element IS, the arm 20 will move downwardly, thus initially returning the shield to the position of Figure 2, and thereafter the strap 28 will again slip relative to the spindle 30, the spring 36 acting to retract the strap.

Below the shield S is a heater H, such as a resistance wire in zigzag formation and suitably supported at its ends. Above the shield S is a bimetal actuator 44 having one end a ounted on 45 a stationary projection 46 of the base l2. The other end is free to warp from the position of Figure l to the positions of Figures 5 and 6, upon being heated to an intermediate and maximum degree respectively. 5

The actuator 44 operates a switch arm 45 pivoted at 48 and carrying a spring arm 50. The spring arm 50 is operable to close the burner switch contacts BS, which in most installations operates a motor M as shown in Figures 7 and 8.

This motor usually blows air and pumps fuel to the burner.

A safety switch SS is provided, and it also is operated by the arm 5|! through a link connection 52. The link is shouldered at 53, and thereby has a lost motion connection with a spring arm 54 of the safety switch through a perforation of which, the left end of the link extends.

To provide snap action for the burner switch BS an armature 56 may be provided on the leaf spring 50, and is afl'ected by a permanent magnet 58 in the usual manner. The burner switch BS and the safety switch SS are connected in the circuit of the motor M by wires 0, b, c, and d. The wires 11 and d are connected with current supply wires e and f.

A room thermostat is illustrated at RT. It may be connected to the secondary of a transformer T and the heater H by wires and h, as in Figure 7, or may be connected as in Figure 8 by these wires with the supply wires e and I, if the room thermostat and heater are designed for line voltage rather than for stepped down voltage of the transformer secondary.

Practical operation In the operation of my burner control system the parts are normally in the position of Figure 1. Upon a call for heat by the room thermostat a circuit is traceable through the following elements in Figures 7 and 8: a, H, RT and h. This energizes the heater so that it causes the element 44 to warp from the position of Figure 1 to the position of Figure 4 in which the burner switch BS has just been closed. This will cause the burner to operate and the element 44 will continue to move but will not yet open the safety switch, because it will be noted that the shoulder 53 adjacent the left end of the link 52 has not yet engaged the spring 54. The switch is designed so that it will take about a minute and a half for the shoulder 53 to engage the spring 54 after the burner switch BS is closed. This period, of course, can be changed as desired by properly proportioning the parts.

If combustion occurs within the minute and a half period, the shield S will be rotated to the position of Figure 5, thus shielding the element 44 from the heat of the heater H. The degree of shielding can be controlled in different ways, maximum shielding being secured by providing a blackened or darkened surface 51 for the upper side of the shield in Figure 3, and a reflecting surface 59 for the lower side. The heat from the heater will then be reflected as indicated by arrows 7', while that of the bimetal element 44 will be absorbed.

If the above described reflecting and absorbing action is carried out to the maximum, then the bimetal 44 will warp to its original position, thus causing intermittent operation of the burner while the room thermostat is in closed position, while if it is reduced to some extent, as for instance by omitting the blackened and reflecting surfaces 51 and 59 respectively, or by providing perforations 60 in the shield S, some heat can still be supplied from the heater H to the bimetal 44 to keep it in the positions of Figures 4 and 5, so that the burner switch will remain closed and the safety switch likewise remain closed, while the room thermostat is in a closed position.

Thereafter when the room thermostat opens, the burner switch will be opened by the loss of heat from the bimetal element 44 and the orig- 75 inal position of Figure 1 will be assumed.

If combustion fails after it is established, the shield S will return from the position of Figure to the position of Figure 6, thereby permitting energization of the heater H to further warp the element 44, as in Figure 6, whereby the safety switch is opened and the burner thus shut down. It will then take some time for the safety switch to be reclosed because of the residual heat opening it further, and the contacts being closed only after the heat has been lost to a sufllcient extent to permit the position of Figure 5 to be resumed. During this period purging of the furnace takes place and the controller is then in position for recycling.

If combustion does not occur in the first place, the shield S will remain in the position of Figure 4, and finally the warp element 44 will assume the position of Figure 6, thus opening the safety switch and the purging period will come into effect as above described. The burner will then recycle. An additional means, of course, can be provided to lock the controller in open position if a number of recycles does not produce combustion establishment.

It is obvious also from the foregoing that numerous changes might be made in the construction, arrangement and operation of the parts, and it is my purpose to cover by my claims any modifications in structure or use of mechanical equivalents, which may reasonably come within the scope of my invention and of the claims.

I claim as my invention:

1. In a burner control switch structure, a normally open switch, a normally closed safety switch operable to de-energize the burner circuit, a slow acting actuator for said first switch and said safety switch for first closing the first switch and then opening the safety switch, means for effecting operation of said actuator and means responsive to combustion if established for arresting the operation of said first means after said actuator has closed said first switch.

2. In a burner control switch structure, 9. normally open switch, a normally closed safety switch operable to de-energize the burner circuit, a slow acting actuator for said first switch and said safety switch for first closing the first switch and then opening the safety switch, an

electro-responsive heating means for actuating said actuator upon energization of said electroresponsive heating means, and means for arresting the operation of said electro-responsive heating means after said actuator has closed said first switch, comprising a shield interposed between said electro-responsive means and said actuator, said last means being responsive to combustion establishment.

3. In a burner control switch structure, a normally open switch, a normally closed safety switch operable to de-energize the burner circuit, a slow acting actuator for said first switch and said safety switch for first closing the first switch and then opening the safety switch, an electro-responsive heating means for actuating said actuator upon energization of said electro- 4.1a a burner controller, a normally open switch, a normally closed safety switch operable to de-energize the burner circuit, a slow acting actuator for said first switch and said safety switch for first closing the first switch and then opening the safety switch, an electroresponsive heating means for actuating said actuator upon energization of said electro-responsive heating means, and means for-arresting the operation of said electro-responsive heating means after said actuator has closed said first switch comprising a shield interposed between said electro-responsive means and said actuator, said last means being responsive to combustion establishment, the side of said shield facing said actuator being heat absorbing.

5. In a burner controller, a normally open switch, a normally closed safety switch operable to de-energize the burner circuit, a slow 2o acting actuator for said first switch and said safety switch for first closing the first switch and then opening the safety switch, an electroresponsive heating means for actuating said actuator upon energization of said electro-responsive heating means, and means for arresting the operation of said electro-responsive heating means after said actuator has closed said first switch comprising a shield interposed between said electro-responsive means and said actuator,

said last means being responsive to combustion establishment, the side of said shield facing said electro-responsive heating means being heat reflecting, and the side of said shield facing said actuator being heat absorbing.

6. In a burner controller of the character disclosed, a normally open switch, a normally closed safety switch operable to de-energize the burner circuit, a warp element responsive to heat and operable upon warping to close said a first switch and then open said safety switch,

a resistance element which, when energized, is

operable to radiate heat to said warp element to cause warping thereof, and means responsive to combustion establishment for arresting the flow of heat from said resistance element to said warp element.

7. In a burner controller of the character disclosed, a normally open switch, a normally closed safety switch operable to de-energize the burner circuit, a warp element responsive to heat and operable upon warping to close said first switch and then open said safety switch, a resistance element which, when energized, is operable to radiate heat to said warp element to cause warping thereof, and meansresponsive to combustion establishment for arresting the flow of heat from said resistance element to said warp element, said means comprising a shield interposed between the resistance element and the warp element upon combustion establishment.

8. In a burner controller of the character disclosed, a normally open switch, a normally closed safety switch operable to de-energize the burner circuit, a warp element responsive to heat and operable upon warping to close said first switch and then open said safety switch, a resistance element which, when energized, is operable to radiate heat to said warp element to cause warping thereof, and means responsive to combustion establishment for arresting the flow of heat from said resistance element to said warp element, said means comprising a shield interposed between the resistance element and the warp element upon combustion establishment, said shield preventing at least a portion of the heat generated by said resistance element from affecting said warp element.

9. In a burner control device, a normally open burner switch, a normally closed safety switch, a bimetal warpelement for closing said burner switch and then opening said safety switch upon being heated, a heater for said bimetal warp element, and means responsive to combustion establishment for at least reducing the heating effect of said resistance element on said bimetal warp element.

10. In a burner control device, a normally open burner switch, a normally closed safety switch, a i

bimetal warp element for closing said burner switch and then opening said safety switch upon being heated, a heater for said bimetal warp element, and means responsive to combustion establishment comprising a shield interposed between said resistance element and said bimetal warp element and temperature responsive means for actuating said shield to its interposed position.

11. In a controller of the kind disclosed, a

heating element, a safety switch, an actuator i for said safety switch responsive to heat generated by said heating element, a shield for shielding the heat of said heating element from acting and means responsive to said actuator upon combustion establishment for moving said shield to its effective position.

12. In a controller of the kind disclosed, a heating element, a safety switch, an actuator for said safety switch responsive to heat generated by said heating element, a shield for shielding at least a part of the heat of said heating element from acting upon said actuator and means responsive to combustion establishment for effecting movement of said shield to its shielding position and responsive to combustion failure to effect movement thereof to its non-shielding position.

BURTON E. SHAW. 

